A9 is the newest contender in the search engine world from Amazon. It's basically a front end to Google, Amazon's book search, Google Images, IMDB, and GuruNet, with some links to Alexa thrown in for good measure. I'm liking it a lot so far.
One of the features is being able to type in searches from my browser, for example a9.com/perl takes you to the search results for "perl". If you log in with your Amazon account, you get access to all your previous searches, and you also get a π/2% (1.57%) discount on your Amazon purchases. There are tabs that enable showing or hiding the different sources of search results which work well. Everything is slick and searching is speedy. It seems as responsive as Google. There's a toolbar for Internet Explorer that gives you bookmark and diary features, I'm hoping that they are able to release a Mozilla version as this looks pretty useful.
See also A9 Launches New Version from John Battelle's Searchblog.
The search for Perl quickly reveals heretofore unknown capabilities of the language.
Of course, the problem with A9 is that with all its personalization features, it can effectively collect much, much more extensive information about you than Google. Obviously, with the advent of Gmail, this anonymity crumbles if you don't clear its cookie. However, A9 can still tie together many more threads of information about you than Google does.
For me, another consideration is that both services' data stores are situated in a country with far weaker privacy laws than those we have in Germany but something called the PATRIOT act to make up for it… which makes the use of A9 particularly precarious, but means I'm not signing up for Gmail either.